igneous
Granite
Granite (Felsic Intrusive Igneous Rock)
Hardness: 6-7 on Mohs scale; Color: typically mottled grey, white, pink, and black; Luster: Dull to vitreous; Structure: Phaneritic (coarse-grained) crystalline; Cleavage: none (though component minerals have their own); Specific Gravity: 2.63 to 2.75.
- Hardness
- 6-7 on Mohs scale
- Color
- typically mottled grey, white, pink, and black
- Luster
- Dull to vitreous
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Physical properties
Hardness: 6-7 on Mohs scale; Color: typically mottled grey, white, pink, and black; Luster: Dull to vitreous; Structure: Phaneritic (coarse-grained) crystalline; Cleavage: none (though component minerals have their own); Specific Gravity: 2.63 to 2.75.
Formation & geological history
Formed from the slow cooling of silica-rich magma deep underground (plutonic). Found in continental crust; ages can range from billions of years (Precambrian) to relatively recent mountain-building events.
Uses & applications
Extensively used in construction for countertops, floor tiles, paving stones, and memorial monuments. Also used as crushed stone for road base and railroad ballast.
Geological facts
Granite makes up the majority of the Earth's continental crust. It is the primary rock found in iconic locations like Yosemite National Park's Half Dome and Mount Rushmore.
Field identification & locations
Identify in the field by its 'salt and pepper' appearance and large, interlocking mineral crystals (visible quartz, feldspar, and mica). Found globally in mountainous regions or where ancient shield rocks are exposed. Collectors look for unique color variations or large crystal inclusions.
